GB2042036A

GB2042036A - Mine roof support

Info

Publication number: GB2042036A
Application number: GB8002370A
Authority: GB
Original assignee: Voestalpine AG
Current assignee: Voestalpine AG
Priority date: 1979-02-14
Filing date: 1980-01-24
Publication date: 1980-09-17
Also published as: ATA113479A; DE3002333A1; US4299517A; DE3002333C2; PL222022A1; AT360936B; YU38180A; FR2449195A1; AU5531280A

Description

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GB2 042 036A

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SPECIFICATION

Mine roof supporting structure

5 This invention relates to a mine roof supporting structure comprising at least one cap extending over one end of a floor frame and supported against the said floor frame by hydraulically operated props, a shield pivota-10 bly linked at one end to said cap and pivota-bly linked at its other end to a link lever which link lever is also pivotably linked to the said floor frame, whereby lowering of the cap by contraction of the said hydraulically operated 1 5 props causes the pivotal point of the shield and link lever to be moved in a direction generally opposite to the direction of extension of the cap over the said floor frame, and a hydraulically operated cylinder-piston ar-20 rangement connected to the said floor frame and operable to effect movement of the said pivotal point of the shield and link lever in a direction generally towards the direction of extension of the said cap over the floor frame. 25 Such mine roof supporting structures are known and commonly used and have the cap protruding over the foreward end of the floor frame facing the mine face because the floor frame must keep free a space for the conveyor 30 means arranged at the mine face and because this conveyor means shall be protected by the cap. It is already known to position the front cap in any height position of the mine roof supporting structure by forcing the link lever, 35 to which the shield is linked, in a direction towards the front end of the floor frame by means of a hydraulic cylinder-piston arrangement. Such constructions only serve the purpose for guiding the front cap and particularly 40 to maintain the front end of the front cap at a constant small distance from the mine face irrespective of different height positions of the mine roof supporting structure. For this reason, the cylinder-piston arrangement required 45 for such adjusting movement was of weak design in said known constructions. In view of the cap protruding in direction to the mine face, the front end of the floor frame is, however, subjected to substantially higher 50 load than its rear end. This has as a result that, particularly with weak mine sill, the front end will sink into the mine sill. The mine roof supporting structure will thus tilt in direction to the mine face and the stability of this 55 structure will be reduced.

The present invention now aims at increasing the stability of a mine roof supporting structure of the kind hereinbefore set forth, and is characterised in that the said cylinder-60 piston arrangement can be supplied with hydraulic fluid to effect movement of the said pivotal point towards the direction of extension of said cap only when hydraulic fluid in the said props has attained a predetermined 65 pressure which is smaller than the final supporting pressure in the said props for a mine roof.

By the practice of the invention an acting force is introduced into the mine roof support-70 ing structure which pulls the front end of the floor frame in upward direction and subjects the rear end of this floor frame to a heavier load via the shield and the link lever. The front end of the floor frame becomes thus 75 partially relieved and the load centre of the floor frame is shifted in backward direction in direction to the old excavation. The stability of the mine roof supporting structure is thus increased and even in a soft mine sill, sinking 80 in of the front end of the floor frame into the mine sill and the tendency of the mine roof supporting structure to tilt in direction to the mine face is counteracted. The hydraulic cylin-der-piston arrangement, by means of which 85 the pivotal point between shield and link lever is fixed in position relative to the floor frame, is according to an advantageous embodiment designed as a tension strut in which the working chamber located at that side of the 90 piston which carries the piston rod (in which the piston rod chamber of the piston) is supplied with pressurizing fluid after having pressurized the props. In this case, the lever system formed of shield and link lever, which 95 is acting like a toggle-joint, is pulled in direction to its stretched position, whereby the load acting on the linking point between link lever and floor frame is increased and the front end of the floor frame is pulled in upward direc-100 tion.

In a preferred feature of the invention, the said cylinder-piston arrangement can be supplied with hydraulic fluid to effect said movement only when hydraulic fluid in the said 105 props has attained a pressure of about 20% of the said final supporting pressure. This has as a result that an equalization in load becomes effective only after the mine roof supporting structure already exerting a certain 110 supporting force and being maintained in position. The arrangement according to the invention furthermore is preferably such that the force exertable on the said pivotal point by the said cylinder-piston arrangement is smaller 115 than the sum of the supporting forces exerted by the said prop(s) on a mine roof, and is more preferably about 30% of the sum of these supporting forces. In this manner the tension force acting on the pivotal connection 120 between shield and link lever serves to a vast extent for equalizing the load of the floor frame whereas the main supporting forces are exerted by the props.

In a particularly preferred embodiment in 125 which a cylinder-piston arrangement is formed of a tension strut, a conduit for supplying hydraulic fluid is connected to the working chamber(s) of the said prop(s), and to the working chamber of the said cylinder-piston 1 30 arrangement via a spring-loaded valve the

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spring of which is of such strength so as to open the said valve at the said predetermined pressure, and the piston surface delimiting the said working chamber is smaller than the 5 surface(s) of pistons within the working chambers of said prop(s) which pistons delimited the working chambers thereof.

By correspondingly prestressing the spring of the spring-loaded valve, the tension strut 10 will thus be made effective only when the props exert part of its supporting force and thus when the mine roof supporting structure is held in position. By giving the piston surface of the hydraulic tension strut, which is 15 subjected to the action of the pressurized fluid, the mentioned dimension in relation to the piston surfaces of the props, the force acting on the pivotal point between shield and link lever is brought into the proper relation to 20 the supporting force exerted by the props.

The invention is further explained with reference to the drawing showing embodiments of the structure according to the invention.

In the drawing 25 Figure 1 shows a side elevation of a mine roof supporting structure,

Figure 2 shows a detail in a section along line ll-ll of Fig. 1,

Figure 3 schematically shows the hydraulic 30 piston-cylinder-arrangements in a prop according to Fig. 1 and

Figures 4 and 5 show modified embodiments, noting that the mine roof supporting structure, which corresponds in its essence to 35 the arrangement shown in Fig. 1, is outlined 1 in straight lines only.

In the arrangement according to Figs. 1 and 2, 1 is the floor frame and 2 is the cap which is supported against the floor frame 1 by two 40 hydraulic props 3. A shield 4 is linked to the 1 cap 2 and further linked to the floor frame 1 at a pivotal point 7 with interposition of a link lever 5 linked to the shield at 6. The cap 2 is formed of a swivelling cap 8 which is (com-45 pare Fig. 2) supported by the props 3, noting 1 that the linking point between the props 3 and the swivelling cap 8 is designated 9. A cap 11 and the shield 4 is pivotally linked to this swivelling cap 8 by means of a pivotal 50 bolt 10. 1

The piston rod 13 of a hydraulic tension strut 14 is pivotally linked to the shield 4 at 12, the cylinder 15 of this strut being pivotally linked to a pivotal point 16 which is 55 located between the pivotal point 7 between 1 link lever 5 and floor frame 1, and the mine face 17.

The hydraulic strut 14 is acting via the shield 4 on the pivotal point 6 between shield 60 4 and link lever 5 and is pulling this linking 1 point 6 in direction to the floor frame, so that the front end 18 of the floor frame 1 facing the mine face is partially relieved from load and the load acting on the pivotal point 7 65 facing the old excavation or old man becomes 1

increased via the shield and the link lever 5.

In Fig. 3 the hydraulic piston-cylinder-arrangements are schematically illustrated. The supply conduit 19 for pressurizing fluid is connected with a working chamber 21 of the props 3 via a check valve 20. Furthermore, this supply conduit is connected via a check valve 23 loaded with a pretensioned spring 22 with the piston rod chamber 24 of the hydraulic tension strut 14. 25 is a changeover valve comprising a ball 26 which on pressure existing in the supply conduit 1 9 is closing a valve seat 27 leading to a conduit 28. On account of the spring 22, the check valve 23 gives a response only after having attained a predetermined supporting pressure. In view of the check valve 20, the props 3 are maintained in position even with no pressure in the supply conduit 19 and in view of the check valve 23 also the hydraulic tension strut 14 is maintained in its position so that after having supplied pressurizing fluid the props 3 and the tension struts 14 are independently one from the other maintained in their positions.

When collapsing the mine roof supporting structure, the piston rod chambers of the props 3 are subjected to pressure via a conduit 29, which when setting the props was connected to the discharge conduit for pressurizing fluid, noting that the closing member of the check valve 20 is lifted off its seat by means of a device 30 subjected by the pressure prevailing in a conduit 29, and, in addition, the piston chamber 32 of the tension strut 14 is subjected to pressure via a conduit 31 previously connected to the discharge conduit, noting that the closure member of the check valve 23 is lifted off its seat under the action of the pressure now prevailing in the conduit 31 and acting on a device 33 controlling this closure member. The conduit 19 is connected to the discharge conduit in this case.

If it is desired to actuate the tension strut 14 indpendently from the props, pressurized fluid is supplied via the conduit 28. The bore 26 of the change-over valve 27 will now be moved in right-hand direction and pressed against the wall seat 34 so that the conduit 28 is separated from the conduit 19. In this manner it is possible to increase the tension force acting on the pivotal point 6 without increasing the pressure once built up in the props 3 in case, with the mine roof supporting structure already supporting the mine roof, the floor frame 1 does sink into the mine sill.

In Figs. 4 and 5 further arrangements are illustrated which allow to pull in foreward direction the pivotal point 6 between shield 4 and link lever 5. In the arrangement shown in Fig. 4, a hydraulic cylinder-piston-arrange-ment 35 is provided in the floor frame for pulling in right-hand direction the pivotal

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point 6 by means of a cable 36 connected to the link lever 5 and guided over a roller 37. In the arrangement shown in Fig. 5, a hydraulic cylinder-piston-arrangement 38 is pivotally 5 linked to the floor frame 1 and to the link lever 5 for pressing the link lever 5 in right-hand direction and thus in direction to the mine face 1 7.

In Fig. 1, a cylinder-piston-arrangement 39 10 is supporting the roof cap 11 relative to the shield 4. This cap 11 is applied to the mine roof by actuating the hydraulic cylinder-piston-arrangement 39.

Claims

15 CLAIMS

1. A mine roof supporting structure comprising at least one cap extending over one end of a floor frame and supported against the said floor frame by hydraulically operated

20 props, a shield pivotably linked at one end to said cap and pivotably linked at its other end to a link lever which link lever is also pivotably linked to the said floor frame, whereby lowering of the cap by contraction of the said 25 hydraulically operated props causes the pivotal point of the shield and link lever to be moved in a direction generally opposite to the direction of extension of the cap over the said floor frame, and a hydraulically operated cylin-30 der-piston arrangement connected to the said floor frame and operable to effect movement of the said pivotal point of the shield and link lever in a direction generally towards the direction of extension of the said cap over the 35 floor frame; characterized in that the said cylinder-piston arrangement (14, 35, 38) can be supplied with hydraulic fluid to effect movement of the said pivotal point (6) towards the direction of extension of said cap 40 (2) only when hydraulic fluid in the said props (3) has attained a predetermined pressure which is smaller than the final supporting pressure in the said props for a mine roof.

2. A mine roof supporting structure ac-45 cording to Claim 1, wherein the said cylinder-

piston arrangement can be supplied with hydraulic fluid to effect said movement only when hydraulic fluid in the said props has attained a pressure of about 20% of the said 50 final supporting pressure.

3. A mine roof supporting structure according to Claim 1 or Claim 2, wherein the force exertable on the said pivotal point by the said cylinder-piston arrangement is smaller

55 than the sum of the supporting forces exerted by the said prop(s) on a mine roof.

4. A mine roof supporting structure according to Claim 3, wherein the said force exertable on the said pivotal point is about

60 30% of the said sum of supporting forces for a mine roof.

5. A mine roof supporting structure according to any of Claims 1 to 4, wherein a conduit (1 9) for supplying hydraulic fluid is

65 connected to the working chamber(s) (21) of the said prop(s), and to the working chamber (24) of the said cylinder-piston arrangement via a spring-loaded valve (23) the spring (22) of which is of such strength so as to open the 70 said valve at the said predetermined pressure, and the piston surface delimiting the said working chamber (24) is smaller than the surface(s) of pistons within the working chambers (21) of said prop(s) which pistons delim-75 ited the working chambers thereof.

6. A mine roof supporting structure according to any of Claims 1 to 5, wherein a conduit (19) for supplying hydraulic fluid is connected to working chamber(s) (21) of the

80 said prop(s), and to working chamber (24) of the said cylinder-piston arrangement, and a change-over valve (25) is provided between the said conduit and the said working chamber of the cylinder-piston arrangement which 85 in one position connects the said conduit with the said working chamber of the cylinder-piston arrangement and which in the other position connects the said working chamber of the cylinder-piston arrangement with a sepa-90 rate conduit (28) for hydraulic fluid whilst closing the connection between the first mentioned conduit and the said working chamber of the cylinder-piston arrangement.

7. A mine roof supporting structure ac-95 cording to any of Claims 1 to 6, wherein a check valve is provided in a conduit for supplying hydraulic fluid to the said prop(s), whereby the said props may be maintained in position in the absence of pressure in the said 100 conduit.

8. A mine roof supporting structure, substantially as hereinbefore described and illustrated in Figs. 1 to 3, Fig. 4 or Fig. 5 of the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd.—1980.

Published at The Patent Office, 25 Southampton Buildings,

London, WC2A 1AY, from which copies may be obtained.